Modify GrBWFillRectBatch to use GrQuad

src/gpu/GrQuad.h

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef GrQuad_DEFINED
 #define GrQuad_DEFINED
 
 #include "SkPoint.h"
 #include "SkMatrix.h"
 
 /**
  * GrQuad is a collection of 4 points which can be used to represent an arbitrary quadrilateral
  */
 class GrQuad {
 public:
+    GrQuad() {}
+
     GrQuad(const GrQuad& that) {
         *this = that;
     }
 
     explicit GrQuad(const SkRect& rect) {
         this->set(rect);
     }
 
     void set(const SkRect& rect) {
         fPoints->setRectFan(rect.fLeft, rect.fTop, rect.fRight, rect.fBottom);
@@ skipping 14 matching lines @@
     }
 
     SkPoint* points() {
         return fPoints;
     }
 
     const SkPoint* points() const {
         return fPoints;
     }
 
+    const SkPoint& point(int i) const {
+        SkASSERT(i < kNumPoints);
+        return fPoints[i];
+    }
+
 private:
     static const int kNumPoints = 4;
     SkPoint fPoints[kNumPoints];
 };
 
 #endif